DE2309449A1 - THERMALLY STABLE AND PRESSURE RESISTANT MICROPOROESE CATALYST CARRIER MADE OF GLASS AND THE PROCESS FOR THEIR PRODUCTION - Google Patents

Description

Thermally stable and pressure-resistant microporous glass catalyst carriers and process for their production

Priorities: March 2, 1972, U.S. Ser. No. 231,346

June 19, 1972 USA Ser. No. 264 081 December 1, 1972. USA Ser. No. 311 191

The invention relates to highly porous glass bodies, in particular to microporous glass particles of high compressive strength and high thermal stability. It also relates to processes for the production of such glass bodies, as well as types of glass that are because of their composition, they are particularly suitable for their preparation by the process according to the invention. In particular The invention relates to a method according to which the compressive strength and the dimensional stability or dimensional stability the porous glass body can be further improved at higher temperatures.

It is known to produce porous glass bodies by heating glass for the purpose of phase separation and dissolving the soluble phase therefrom. Processes of this type are described in U.S. Patents 2,106,744 and 2,221,709. According to this process, porous glass is produced from an alkali-boron-lime glass in such a way that the glass is separated into two phases by heating, namely into an insoluble phase rich in silicon dioxide and a soluble phase rich in boron oxide and alkali. This latter phase is soluble in acid and can be dissolved, wherein the insoluble phase, remaining as a solid cellular structure in the mold which had the glass before the treatment. It has been suggested this

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to use porous structures made of silicon dioxide as a carrier for catalysts. Furthermore, the use of porous Glass as a support for catalysts is also mentioned in US Pat. Nos. 2,461,841, 2,480,672, 2,834,738 and 2,835,367. However, its use for this is noticeably limited by the fact that the highly porous structures are still used today could not give high mechanical strength and thermal stability. For use as a catalyst carrier, for example In fluidized beds or in the mufflers of motor vehicles, it is disadvantageous if the highly porous Glass has poor mechanical strength and shrinks under the high temperatures to which it is exposed.

The invention now provides a method by which porous glass bodies can be produced with improved compressive strength and improved dimensional stability at higher temperatures. The process consists in that a glass with a low silicon dioxide content and a high borate content, a glass which consists of 30 to 50, preferably 38 to 46% by weight of SiO ₂ , 40 to 55, preferably 40 to 52% by weight of B ₂ O ^,

5 to 15, preferably 8 to 12% by weight R ₂ O and

0 to 4, preferably 0 to 0.3% by weight Al ₂ O, where R is an alkali metal, broken down into a silicon dioxide-rich and a borate-rich phase, from which the phase-separated glass is used to produce a porous glass, the borate-rich phase with water slowly removed in sufficient quantities, the porous glass was then washed with an aqueous acid solution to remove the alkali oxide and the borate from the silicon dioxide framework and the alkali and borate-poor microporous glass body was removed from acid and any residues of the soluble ones that remained in the pores after the acid treatment with deionized water Phase washes free.

You can improve the compressive strength of the porous glass body and its dimensional stability at higher temperatures.

make sure that the vitreous bodies are used before they are

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manure, for example as a support for catalysts, is slightly pre-shrunk. For this purpose one can short the vitreous expose to the maximum temperature they will be exposed to in practice. For example, a satisfactory one is achieved Effect if you hold it for half an hour to five hours at a temperature of 400 to 1000 ° C. If the porous glass body according to the invention is heated in this way, its volume shrinks by about 5 to 20% one, and surprisingly most of the total shrinkage occurs, i.e. 70 to 90%, about during the two first hours of heat treatment. Beyond this time, the shrinkage continues under the influence of the above high temperatures only to a small extent. The pre-shrunk porous glass bodies therefore offer security bordering guarantee that it will not shrink any further when used as a catalyst carrier in the exhaust pipe subject.

The dimensional stability of the porous glass body at higher temperatures can be further improved by the fact that the porous glass is treated with tin oxide.

The porous glass bodies according to the invention consist, determined analytically, from

at least 96, preferably 97 "to 99% by weight SiO ₂ , less than 4, preferably 1 to 3% by weight IM) - ,, less than 0.05, preferably 0 to 0.03% by weight of an alkali oxide and less than 0.4, preferably 0 to 0.15% by weight

For purposes that require high dimensional stability at higher temperatures and high compressive strength, for example when used as a catalyst carrier in the exhaust stoppers of motor vehicles, one can According to the invention, produce porous glass bodies that are exposed to a temperature of 980 ° C. for 24 hours, less

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than 25% of their volume by shrinking and less than 3096 lose their surface. They have a compressive strength of at least 1.4 kg / cm abs (20 psig).

For purposes in which the pore volume and the pore size are important, porous can be used according to the invention Vitreous with a pore volume of 0.5 to 0.7 cm per Gram and a mean pore diameter of 200 to 1000 fi. The porous glass bodies have a compressive strength

from about 0.35 to 1.4 kg / cm abs and _ ζ own, for 24 hours exposed to a temperature of 760 ° C, a volume loss due to shrinkage of about 10 to 20%.

In the drawing shows

1 shows a device operating with a compressed air cylinder for measuring the compressive strength of the microporous glass beads according to the invention and

FIG. 2 the device according to FIG. 1 in a schematic representation.

One can use the boron-lime glasses suitable for the purposes of the invention melt according to known methods. As a rule, the raw materials such as quartz sand, boron oxide and alkali oxides are mixed and, optionally, clay and melts them together. If you prefer to use the raw materials in a form in which they easily form a melt when mixed with one another, the oxides can, in addition to their free form, also in the Other suitable compounds may be used. Examples of such compounds are alkali carbonates, borates and called aluminates.

A glass is particularly suitable for the purposes of the invention, which, before phase separation and washing, has the following composition:

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30 to 50, preferably 38 to 46% by weight ₂ 40 to 55, preferably 40 to 52% by weight B ₂ O ₅ ,

5 to 15, preferably 8 to 12% by weight of R ₂ O and • 0 to 4, preferably 0 to 0.3% by weight of Al ₂ O ,. (In the table, R means alkali)

During the phase separation of the glass, silicon dioxide forms the insoluble phase and the main component in the glass skeleton of the porous glass body according to the invention. The silicon dioxide content of the glass should not exceed 30% , because otherwise the porous glass has too little pore volume to still be usable as a catalyst carrier. Furthermore, if the silicon dioxide content is too high, it is difficult to dissolve the borate and the alkali oxide out of the silicate skeleton with the acid. The consequence would be a deterioration in the thermal stability of the catalyst support, which shows itself in greater shrinkage or in a loss of surface area of the porous glass when it is exposed to higher temperatures, for example 16 to 24 hours at a temperature between 850 and 980 ° C. In order to have a large pore volume, the glass should have a low silicon dioxide content, preferably a silicon dioxide content of about 38 to 45%. However, the silicon dioxide content should not be below 30% by weight, because with such a composition of the glass after the phase separation and after the dissolving out of the soluble phase, porous structures with relatively low mechanical strength (compressive strength) are obtained.

The B ₂ 0 - content of the glass is related to its SiO ₂ content. In general, it increases as the SiO ₂ content decreases. The SiO ₂ content to the B ₂ O content preferably has a ratio of 1: 1 to 1: 1.3. The B ₂ O ^ content should not exceed 55% by weight of the glass mass, because otherwise the microporous glass bodies will have a relatively low compressive strength. Conversely, the

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not be less than 40%, because otherwise a glass cannot be leached well with water and has too small a pore volume to be suitable as a catalyst carrier and to ensure a high catalytic effect. In general, a lower Si0 ₂ : B ₂ 0, ratio results in a larger surface area and a larger pore volume.

The alkali oxide is used as a flux to lower the melting temperature of the glass. Lithium oxide, sodium oxide and potassium oxide are suitable, either individually or mixtures of two or three of these compounds. Sodium oxide is preferably used. If the glass mass contains less alkali oxide than according to the table above, the melting temperature of the glass can be too high from an economic point of view. The alkali oxide content is also related to the mechanical strength of the porous glass body. It has been shown that both elrr z \ a high and a low alkali metal oxide content to ^ u porous glass bodies having low mechanical strength lead. Without being bound by theory, it is believed that the alkali oxide plays an important role in phase separation and in leaching out the soluble phase. On the other hand, if the alkali oxide content is too high, the silicon dioxide phase and the borate phase dissolve too much into one another during the heat treatment and the borate phase contains too much silicon dioxide when it is dissolved out of the silicon dioxide skeleton. The result would be a skeleton or framework that is poor in silicon dioxide and therefore mechanically weak and easily shattered.

The following embodiment of the invention is intended to show which effect the alkali oxide component has on the compressive strength of porous glass beads. Used glass beads are produced in the following composition in the manner described in Example 1 are ι

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SiC ₂ 40 45 33 46 54 48 Weight% B ₂ O ₃ 40 44 46 48 Weight% Na ₂ O 20th 11 8th 4th Weight% Compressive strength 0 1, 1, 0 kg / cm abs

The number "O" in the first column means that the pearls after the washing process disintegrate, and in the fourth column that the pearls have numerous fine cracks in their surface demonstrate.

It has already been said that the alkali oxide of the glass melt is mainly added as a flux to reduce the melt temperature. Other fl uids known and used in glass manufacture can also be regarded as being equivalent to the alkali oxides as fluxing agents and being usable as such for the glass masses of the composition according to the invention. Examples of metal oxides other than alkali oxides which can be used as flux in the practice of the invention are the alkaline earth oxides, in particular calcium and magnesium oxides, and other metal oxides such as BaO, PbO, CdO, S ⁿ .O and ZnO. However, the alkali oxides are clearly used as flux because of their excellent action and because they can be easily washed out of the silica skeleton.

If required and desired, up to 4% by weight of alumina can be added to the glass mass. It is believed that the addition of alumina to a glass with a high silicon dioxide content, for example an SiO ₂ content of about 46 to 50%, and a low borate content, for example a B ₂ O content of about 35 to 40 %, reduces the risk of stress corrosion in the silicon dioxide skeleton during washing to a minimum. Stress corrosion is understood to be the state that occurs when the outer or leached part of the glass bead comes under tension due to the shrinkage of the silicon dioxide-rich skeleton and its inner or not leached part is pressed together. The tension becomes too

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large uiid / or if there are micro-flaws, then cracks form on the surface. Alumina slows down the phase separation and leads to the formation of smaller pores and thus less stress corrosion. This reduces the likelihood that fine cracks will form which, under tension, will expand into severe cracks. Furthermore, by adding alumina to the glass masses, porous glass bodies with an enlarged surface are obtained. However, these glass bodies also have the highest loss of surface when used at high temperatures. In the case of the glass compositions which contain approximately 38 to 46% by weight of SiO ₂ and 40 to 52% by weight of B ₂ O and are preferably used, the addition of alumina results in no particular advantages. It is therefore preferable not to use it. In no case, however, should the addition of alumina be greater than about 4% by weight, because glasses with a higher alumina content are generally difficult to break down into their phases and leach out.

According to the analysis, the glass mass according to the invention generally contains about 0.15 to 0.3% Al ₂ O. You write this one

': Contamination of the silica with alumina too. Therefore, while the calculated glass mass does not _{contain any Al 2} O, a quantitative dimensional analysis occasionally finds up to 0.3% O.

After the glass has been melted from its constituent parts, it is converted into particulate form. The particle formation can take place either directly from the glass melt or in such a way that the glass is first formed into dimensionally stable pieces and these are then mechanically comminuted. The particle size can be controlled by crushing or grinding the pieces of glass and then sieving the goods with sieves from the US standard series of sieves, the glass can also be converted into particle form by directing the glass melt with a suitable gaseous or liquid agent deterred. Examples of such agents are air or liquids, such as water and oils. If you have the glass

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If particles are produced directly from the molten glass in this way, they usually have the desired pearl shape and do not require any further shaping. However, if the glass is crushed mechanically or directly Quenching the melt into particulate form requires further deformation or bead formation.

Bring the irregularly shaped particles that way in the most common spherical or bead shape for their use as a catalyst carrier, that they are inclined by one rotating and lined with alumina rotary kiln. In its middle part there is the rotary kiln a temperature of about 925 to 1100 ° C. To prevent the particles from adhering to the lining of the furnace To prevent this, they can be mixed with boron nitride or soot. For example, 1 part by weight of boron nitride can be added 74 parts by weight of glass prevent sticking.

The preferred bead size used for the porous catalyst support depends on the intended use of the catalyst . For example, a catalyst support should have a bead diameter of about 0.1 to 0.3 mm when used in a fluidized bed, a bead diameter of about 1 to 2 mm when used in a fixed bed and a muffler when used as a catalyst support Motor vehicle lift a pearl diameter of about 2 to 4 mm. In general, particles with a full diameter of about 0.05 to 5.0 mm can be easily produced.

Once the pearls are made in their respective size, a phase separation is carried out on them. For this purpose, it is heated to around 420 to 700 ° C and held for 1 hour up to 64 hours at this temperature. Through this heat treatment, if done properly, the glass becomes more or less completely separated into two phases, one of which is very rich in boric oxide and alkali and in water and acids is soluble, and the other phase is very rich

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on silicon dioxide and in water and, with the exception of hydrofluoric acid, is insoluble in acids. In the state of Phase separation, the glass has a bluish opalescence in most cases.

During the heat treatment, the phases to be separated have such viscosities and their proportions by volume are such that no separation in the usual form of an emulsion or a system of droplets dispersed in a second phase takes place, but a separation into a continuous thread-like structured phase, embedded in the insoluble Phase. The soluble phase, since it is continuous, can be completely dissolved out of the insoluble phase. After the soluble phase has been dissolved out, a solid, porous framework remains from the original shaped glass body.

The temperature for the phase separation and the temperature to be used for it Time are mainly dependent on the desired pore size and pore distribution. Sample catfish received beads with a mean pore diameter of 50 to 200 S when considering the heat treatment of the glass beads at low temperatures, for example at 420 to 500 ° C, and with short treatment times of, for example Works 1 hour to 8 hours. Washed out and treated properly, these pearls have a thermal effect Stability and compressive strength that make them particularly suitable as a catalyst carrier in the mufflers of motor vehicles make suitable. With longer treatment times and at higher temperatures, for example treatment times of 8 up to 24 hours and temperatures from 580 to 650 ° C, one obtains pores with diameters in the range from 200 to 1000 &. By careful selection of the water leaching conditions, as discussed later, it is possible to Manufacture pearls with adequate strength and thermal stability in the 600 to 1000 Å range. Pearls of this type are weaker than those with smaller pores and

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not as thermally stable as this one. Large pore size pearls have a compressive strength of 0.35 to 1.4 kg / one abs and thermal stabilities which, when the beads are treated at 760 ° C. for 24 hours, have a degree of shrinkage of 10 to 20 VoI.96 correspond. However, such pearls are for Purposes for which high thermal stability and high compressive strength are not required, very suitable, for example in crude oil refining and in cryogenic fixed beds. In general, however, it is inconvenient to use the To carry out heat treatment at a temperature of more than 700 ° C, because at such high temperatures the two phases tend to mix and the glass beads tend to form stress cracks and thermal instability, which are both causes the pearls to shrink excessively and to lose a significant part of their surface area when they are removed exposed to higher temperatures for a longer period of time.

In the case of the glass compositions preferably used, of the one according to the invention Composition can be a very effective phase separation also toiit a treatment at low temperatures, i.e. at temperatures of 460 to 500 ° C, and with short treatment times, for example those of 3 to 5 Hours, bring about. After washing, the pearls have a large pore volume with a relatively small pearl size and, being free from stress cracking, good mechanical strength. With the glass masses in their composition are outside the preferred range, i.e. those comprising clay and, in a major amount, an alkali oxide contain, the greatest porosity is achieved without the formation of stress cracks and with high mechanical strength when the pearls are kept for a relatively long time, i.e. 16 to 64 hours, under relatively low temperatures Holds temperatures, i.e. temperatures of 450 to 500 ° C. Temperatures below 450 ° C are inappropriate because the glass has excessively high viscosities at such low temperatures that no longer allow an effective phase separation.

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After the heat treatment and phase separation, the glass beads are cooled and subjected to an extraction process. In this process, the glass beads are treated with water in a first stage and with acid in a second stage washed. In the first stage, the soluble borate-rich phase is extracted from the pearls in a water bath. The water of the solution bath should have a temperature of about 80 to 100.degree. C., preferably 90 to 100.degree. By doing As the temperature drops below 80 ° C, the extraction becomes weaker. This must be done by extending the Extraction time to be compensated. On the other hand, the solubility of the borate-rich, i.e. the alkali borate salts, increases such as sodium pentaborate, and boric acid containing phase with temperature. At a water temperature of 90 to At 100 ° C, the borate-rich phase has almost maximum solubility. Complete solubility of this phase is, as explained in more detail below, in connection with its Recycling and reuse are important. The duration of the water wash depends on the temperature of the water bath and on the size of the glass beads. It has been shown that with a bead size of 2 to 4 mm temperatures in the range from 90 to 100 ° C and a treatment time of about 4 to 24, preferably from about 10 to 12 hours, are suitable.

To dissolve the borate-rich, soluble phase 'from the Glass beads should be applied to one volume of the glass about 2 to 8 volumes of water. With a smaller one The water-to-glass ratio slows down the dissolution process. Conversely, a higher ratio does not result in any special advantages.

After treating the glass in the water washing stage the aqueous solution containing the soluble phase, hereinafter referred to as "extract", is separated from the beads, directs them into a separating device, for example into one An evaporator or a cold trap and separates the water from the borate salts. You can use the borate salts

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reuse in the manufacture of molten glass. The water can also be used to wash out the glass beads, used and returned for this purpose. The hot extract is expediently passed into at 20 to 25 ° C. a cold trap. About 80% of the borate salts are deposited here. The one containing the remaining borate salts in solution aqueous solution is recycled for reuse when washing the glass.

After washing with water, the glass beads, while still wet, are subjected to a treatment in an acid bath in a second stage. Suitable acids for this are mineral acids, such as hydrochloric acid, sulfuric acid and nitric acid, or organic acids such as oxalic acid, in the form of dilute solutions, advantageously from 0.1 to 3 normal solutions. The concentration of the acid, the duration The acid wash and the temperature at which it is done depend on the amount of the silicon dioxide rich skeleton of alkali oxide to be removed and the speed with which this is to be removed, away. Acids are used with a higher normality, i.e. with a normality of 2 to 3 if the previous one Phase separation has remained incomplete, i.e. when there is significant amount of alkali oxide in the silica skeleton and borate remained. If, on the other hand, the previous phase separation occurred to the point of completeness is, i.e. if borate and alkali oxide are for the most part arranged in the corridors of the silica skeleton, is sufficient . the use of acids with a lower normality, i.e. a normality of 0.1 to 0.3. Generally leads washing with acids for at least half an hour, expediently for about 2 to 4 hours at one temperature from about 80 to 100 ° C. It has been shown the duration of the acid wash and the temperature used not decisive to a measurable degree for the stresses developing in the pearls. Therefore, at the ex-

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. traction with acid for a long time at relatively high levels Working temperatures. However, it has also been shown that there is no particular advantage in acid washing to work longer than four hours.

For acid washing, about 1 to 8 parts by volume of acid should be used on one part of the glass. This Ratio fluctuates to some extent with the normality of the acid used. In general, the ratio is the acid to the glass with increasing normality of the acid smaller,

According to the water-acid process described, highly porous and large-pored beads with a larger surface can be made with produce higher compressive strengths and better thermal stability than comparable pearls that have been washed only with water or only with acid. It is believed to have an excellent effect the two-stage water-acid wash explains the fact that the first wash with water increases the extraction rate the borate-rich phase slows down and that the silica-rich phase Phase is extracted to a lesser extent. Here, the silicon dioxide phase is subject to a lesser one Shrinkage. Furthermore, the slowed washing speed allows the pearls time to part of the build-up of tension break down, and leads to porous glass bodies of high mechanical strength. By the second wash with a mineral acid a large part of the alkali oxide that was not removed during washing with water is removed from the silicon dioxide structure. and amount of borate. Since the alkali oxide and the borate lower the softening temperature of the silicon dioxide3, it is believed that their removal significantly improves the thermal stability of the porous glass bodies.

After the two-stage water-acid washing process, it is also possible to use the extract from the first treatment stage Recover alcaliborate salt and boric acid and use both components again in the manufacture of glass melts

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use. An extract containing boric acid and alkali oxide could not, if it comes from an acid wash, because of the contamination of the anion by the mineral acid can be recycled in the same way. If you use ordinary mineral acids, such as hydrochloric acid, sulfuric acid and nitric acid, chlorine would be added during the removal of the water and the melting of the glass, Sulfur dioxide and harmful nitrogen gases are released and create serious pollution problems.

The frequent recycling of the borate-rich phase makes it possible to use more than 96% by weight of silicon dioxide in the production containing porous glass body to be assumed essentially only from glass. This has the advantage that for melting little energy is required, so that there are no pollution and sewage problems due to the dissipation of the borate salts arise and that the costs for the starting materials are drastically reduced.

After the acid treatment, the glass is washed to remove the remains of the soluble phase and any contaminants to remove soluble substances, for example iron, which may have reacted with the acid. To this end the glass beads are placed in running tap water or preferably in deionized water for about 1 to 4 hours Water, so that all pores of the glass are exposed to the action of water. Washing in deionized is preferred Water because it has been shown that it can give the glass beads a better thermal stability than with tap water. In other words, it has been found that glass beads washed with deionized water subject to less shrinkage and less loss under long-term thermal stress have on the surface as glass pearls that are washed with tap water. After washing, the glass becomes.-pearls initially to remove the water, usually at a temperature of 80 to 100 ° C in a convection oven

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dried and then dried for one hour at 760 ° C. to remove the chemically bound water.

When viewed with the naked eye, the microporous glass beads have the original shape of the solid glass beads. Under When viewed under an electron microscope, the glass beads are very porous and the pores of each bead are interconnected .

According to an elemental analysis, the glass beads consist of

At least 96% by weight, preferably 96 to 99% by weight SiO ₂ , less than 4% by weight, preferably 1 to 3% by weight B ₂ O, less than 0.05% by weight, preferably 0 to 0.03% by weight .% one

Alkali oxide and less than 0.4 wt. %, Preferably 0 to 0.15 wt.% Al ₂ O ,. The latter component is present as an impurity, although Al ₂ O has not been added to the starting mixture.

The microporous glass beads have in a commercial automatic device according to the method of Braunauer, Emmett and Teller measured their nitrogen adsorption, a high porosity and a large surface area. More details about this method, usually called the BET method, can be found in that of S. Braunauer in Vol. 1 of Princeton University Press, 1943, entitled "The Adsorption of Gases and Vapors "published work. Here, the glass beads have a pore volume of at least 0.35 ccm / g and more, namely from about 0.40 to 0.70 ccm / g and a surface area of at least 100 m / g, as a rule from 200 to 400 m / g. Their pore diameter, determined by electron microscopy, is between 50 and 1000 ft. It hangs in each particular case depends on the type of heat treatment used for the phase separation. It should be noted that the Pore diameters are mean values which lie in a relatively narrow range. As it turns out, are included each assumed mean pore size 50 to 60% of the pores

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within a range of - 20% of the assumed value. For example, have an average pore size of 100 Å 50 to 60% of the pores have a diameter of 80 to 120 pp.

In addition to having a high porosity and a large surface area the microporous glass beads according to the invention, measured by their compressive strength and thermal stability at 980 ° C, surprisingly good mechanical and thermal properties.

The compressive strength of the microporous glass beads is measured in kg / cm abs. expressed by the air pressure under which the Catalyst disintegrates under certain test conditions.

The test of the glass beads for their compressive strength consists, briefly explained, in the fact that one of a certain number of Beads of approximately the same size place one bead each on the anvil of a device operating with a pressure cylinder of the type shown in Fig. 1 and pounded with an air operated piston. The required for this Air pressure is measured precisely and converted into kg / cm abs using a prepared calibration curve. The compressive strength of the Perlen is expressed in the mean value of the converted pressure values.

To determine the compressive strengths, one works with the the following devices and in the manner described below.

1. device ; One uses

(a) a mixing device: any mixing device of the appropriate size that has been tried and tested in practice is suitable. Recommended a mixer for samples of 3.8 liters and less, a column mixer for samples of 3.8 to 7.6 liters and a drum mixer for larger samples;

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(b) a micrometer;

(c) a muffle furnace equipped with a temperature measuring device and a temperature controller;

(D) a device operating with a compressed air cylinder according to FIG. 1, which, as shown in FIG. 2, with an electric System and an air circulation system is equipped;

(e) a pair of tweezers.

2nd sample:

A sample suitably prepared in the composition characteristic of the invention is used of the catalyst carrier. Typically, at least a 3.8 liter sample of the catalyst support is available for testing necessary.

3. preparation of the sample ;

(a) Mix the sample thoroughly before analysis, dry it for 3 hours at 121 ° C or, if necessary, under modified conditions Conditions in a muffle furnace and cool them in a dryer containing anhydrous calcium sulfate;

(b) Take ten whole particles from the sample at random, measure their diameter with a micrometer, and place the maximum and minimum value as well as the mean value fixed;

(c) Preferably, about 40 particles of approximately mean diameter are removed from the sample for testing.

4. Preparing and setting up the device :

(a) The main line for the energy supply and the main line for the air supply are switched on and the needle valve is set the air supply line so that, according to the display on the recorder, an air pressure of 1.75 kg / cm after 8.6 seconds and an air pressure of 3.5 kg / cm is reached after 17.6 seconds.

(b) Insert an anvil of appropriate height into the opening in the bottom of the device. The height of the anvil is determined by the diameter of the particles to be tested. It must be dimensioned so that the descending piston hits the microswitch

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releases and releases the air pressure when the particle is crushed. If one uses the right anvil, it should an adjustment of the microswitch will not be necessary, (c) If necessary, in order to determine the optimal height of the anvil, with several particles on the point 6 (b) and 6 (c), trial tests are carried out. When an anvil of the desired height is not available the microswitch must be arranged in relation to the anvil used so that it is triggered when the Particle is crushed.

5. calibration ;

The air pressure indicator is calibrated using a suitable procedure. Recommended, but not mandatory, is a procedure that consists in inserting a strong metal rod through the opening of the anvil, the rod with its lower one End with the bowl of a "platform balance" in contact, aligns the rod so that it is the piston touches, turns on the power and air supply to the device and precisely measured air pressures on the piston applies. Draw each of these air pressures readable by the recorder and the corresponding ones displayed on the scales Weight values and plots the values read by the recorder in a calibration curve against the displayed weights away.

6. Working method ;

(a) Take the measurements according to Sections 3 (b) and 3 (c) and set up the apparatus according to Section 4.

(b) A dried particle is placed on the anvil with tweezers and the plunger is moved by hand below, so that he touches the forceps, carefully withdraws the forceps, leaving the plunger in this way on the Particles rest.

(c) You turn the toggle switch on so that the piston crushes the splitting, then turn the toggle switch off immediately,

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to trigger the airflow and bring the piston manually back to its upper position. Clean the anvil and plunger before attempting the next particle a brush.

(d) It is checked Each of the particles in the manner described in (a) _f (b) and (c) of this section way.

7. Determination of results ;

(a) One counts each one on the recorder for the air pressure displayed values, i.e. preferably forty values, using the calibration curve prepared beforehand in kg / cm abs.

(b) The mean of all converted pressure values is determined and the mean value for the compressive strength is obtained.

Determined by the measurement method described above, the glass beads produced according to the invention have a Compressive strength of at least 1.4 kg / cm abs (20 psig), in

usually 2.1 kg / cm abs and more for pores with a diameter of 50 to 200 8. Glass beads with a mean pore size exceeding this range, ie a pore size in the range from 200 to 1000 Å, have lower compressive strengths, for example those from 0.35 to 1.4 kg / cm abs.

A measure of the thermal stability of the glass beads can be obtained if you combine the previously dried beads in one Muffle furnace 24 hours one. Temperature of 980 ° C and after the pearls have cooled down, measure the loss of surface and volume. Denotes the loss of volume of the pearls is called volume shrinkage. In summary, it should be said that the microporous glass beads according to the invention, treated in the manner described above, have pore sizes of 50 to 200 Å and less than 30% of their original size Surface and shrinkage less than 25% of theirs Lose volume. Glass beads with larger pores, i.e. pores in the range from 200 to 1000 S, are not in the same place

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Dimension thermally stable. If they are exposed to a temperature of 760 ° C for twenty-four hours, they lose about 10 to 20% of their value Volume through shrinkage.

The compressive strength and the thermal stability of the porous glass body according to the invention can be increased by that the pearls are allowed to shrink slightly. Since this shrinkage usually takes place before the porous glass body, for example as a catalyst carrier, are used in practice, it is referred to below as preshrinking.

Pre-shrinking is carried out in such a way that the porous glass body, for example in the form of beads, is briefly exposed to a higher temperature, ie a temperature of 400 to 1000.degree. C., preferably a temperature of about 800 to 1000.degree. By a suitable choice of temperature and the heating time may be the glass beads without excessive loss of surface area and pore volume to at least 7096 and to more than 90% of the total shrinkage pros _N shrink which they are subject as a catalyst support in practical use. In other words, after pre-shrinking, the glass beads do not shrink further by more than 10% of their volume when used in practice. The volume shrinkage is determined by the amount of loss of compressed bulk volume. It has surprisingly been found that, in order to bring about the desired pre-shrinkage, the porous glass body only needs to be exposed to the required temperatures for a short time, ie up to five hours, expediently even less than two hours *.

If the porous glass body is to be used as a catalyst carrier at higher temperatures, for example in the mufflers of motor vehicles, in which they contain temperatures from 800 to 1000 ° C, they should also be used at these temperatures, i.e. at around 900 to 1000 ° C.

309836/1120

be shrunk so that they have the dimensional stability required at such heat levels. If, on the other hand, they are intended for use at lower temperatures, for example for use in a catalytic cracking plant which is operated at temperatures of 400 to 500 ° C., then a short pre-shrinkage in this temperature range will also suffice for the particles that are used in this case to give the necessary dimensional stability. Depending on the temperature to which the particles as catalyst particles are to be exposed in practice, the pre-shrinkage can therefore be carried out at a temperature of. Perform 400 to 1000 ^QC . The upper temperature limit of 1000 ° C should therefore not be exceeded, because at higher temperatures the micropores are at risk of collapsing, which would result in a drastic reduction in the surface and the pore volume of the glass body. Conversely, the lower temperature limit of 400 ° C. should not be fallen below, because otherwise the shrinkage achieved in a reasonable time would be too small to be of practical importance.

'. It is believed that it is due to the particular physical properties of the microporous glass beads that they can be successfully pre-shrunk by only brief exposure to high temperatures. The microporous pearls have a low alkali and borate content because the two components are largely dissolved out of the silica skeleton. This created tiny cavities in the silica skeleton, which are active sites for the adsorption of hydroxyl ions. At relatively low temperatures, for example at temperatures of 400 to 760 ° C., the microporous beads give off chemically bound water, as is evident from their high weight loss. This creates cavities the size of an atom or a little larger. Under the short-term exposure to medium and high temperatures, these fall in the skeleton

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The voids located in the pearls come together, whereby a strong initial linear shrinkage occurs. On the initial shrinkage, caused by the collapse of the interconnected main pores, is followed by another Shrinkage at a much slower rate. In order to cause these main pores to collapse, a very high temperature i.e. a temperature close to the annealing temperature of a 96 to 99% silica material is required. Further heat treatment therefore only leads to low shrinkage.

The pre-shrinking changes the physical properties of the microporous glass beads is not essential. The pearls lose about 5 to 20% of their volume, about 10 to 25% of their surface and about 5 to 20% of their pore volume. Her. Compressive strength is about 2.1 to 4.9 kg / cm abs increased and their pore diameter slightly enlarged. Their bulk density increases from about 0.60 to 0.70 g / ccm.

The surface loss occurring at the beginning has in practice an advantageous effect with regard to the utilization of the catalyst. During the manufacture of the catalyst if the porous beads are impregnated with a catalyst solution, whereupon the solvent is allowed to evaporate, so that the catalyst is deposited in the pores of the porous glass body. The initial surface loss will be caused by the collapse of the tiny cavities in the silica skeleton. Although these tiny Voids, measured by nitrogen adsorption, the Enlarge the surface of the glass beads, but from a catalytic point of view they play a minor role because they are at high temperatures collapse quickly. Therefore, the catalyst mass flowed into these cavities either becomes in the silica skeleton be enclosed or inactivated after a short catalytic use at high temperatures. this leads to of course, to losses of the catalyst substance, for example a noble metal. If, on the other hand, the micro-

309836/1120

porous catalyst support is first pre-shrunk by a heat treatment, then the tiny micropores for each catalyst solution are closed so that the catalyst can only be deposited in the main pores connected to one another.

The dimensional stability of the Glass beads increased significantly at high temperatures. Thus, according to the invention, pre-shrunk glass beads have a loss of volume read after 24 hours of treatment at 980 ° C, dimensional stability three to four times higher than non-shrunk Pearls.

In the following table (I) are those pre-shrunk according to the invention Glass beads and non-shrunk glass beads are juxtaposed with one another in a number of their properties.

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Table I Comparison of Physical Properties of Preshrunk and Unshrunk Glass Beads

Preshrunk at 980 C for 1 hour

not-shrunk

analysis

Particle size pore volume

medium pore size

surface

Volume shrinkage after 24 hours at 9800 c

Compressive strength

Further Weight% 5 cc / g than 4 more preferred
area Together
settlement Weight 96 % Together
settlement area S. than 0.05 97-99 SiO ₂ wide area 4th more preferred
area SiO ₂ at least 96 than 0.4 1-3 B ₂ O ₃ at least 0.05 96-99 B ₂ O ₃ fewer 2 - 4 mm 0-0.03 Na ₂ O less than 0.4 1-3 Na ₂ O fewer 0 Al ₂ O ₃ less than 0-0.03 Al ₂ O ₃ fewer 2 - 4 mm less than 0 a little less than 0.35 - 0 0.25 - 0, 50-1000 , 7 cc / g 50-1000 S.

100-350 m ² / g

3 - 10% (pore size 50 - 200 S)

2.8 - 4.9 kg / cm abs (pore size 50 - 200 X)

- 400 m ² / g

- 25% (pore size 50 - 200 S)

1.4 - 2.8 kg / cm ² abs
(Pore size 50 - 200 S)

As already stated, the porous glass bodies according to the invention, especially in the form of particles, can be used as catalyst supports. The porous particles can be impregnated with the catalyst by introducing them into solutions of the catalyst or treating them with vapors from which the catalyst is deposited in the pores of the particles. For example, if the catalyst used is a difficult-to-melt metal oxide such as SnOp, or a noble metal such as platinum or palladium, or another metal oxide such as TiO ₂ , V ₂ O ₅ , Cr ₂ O, FeO, CoO, NiO ₂ or CuO , 'is used, impregnate the porous particles with a solution of the metal salt, which gives off the desired metal oxide or noble metal when heated. Examples of such metal salts are metal chlorides, metal nitrates, metal acetylacetonates and metal carbonyls. If the catalyst is to be a metal, the applied metal oxide can be subsequently reduced by passing a stream of hydrogen over the catalyst support.

Tin oxide (SnO ₂ ) is particularly suitable as a catalyst in connection with the porous glass bodies according to the invention, since, as has been shown, it gives the glass bodies increased thermal stability as a carrier. This is surprising in that other metal oxides such as Al ₂ O ,, Cr ₂ O, and ZrO ,, do not have the same effect.

The amount of deposited in the pores of the tin oxide should be between about 0.5 and 10 wt.%, Preferably between about 1 and 5 wt lie.%. It is determined by the pore volume of the particles and the concentration of the catalyst solution. For example, if you want to _{deposit about 1.5 wt.% SnO 2} in the pores of a porous glass body with a pore volume of about 0.5 ccm / g, the particles should be about 15 minutes in about 150 g SnCl ^ '5H ₂ O on a Liters of water containing solution are soaked. After impregnation , the particles should be kept at 100 ° C to remove the water

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dried and then used to convert the tin chloride to tin oxide be calcined.

It is useful to remove the porous glass particles prior to impregnation to pre-shrink with the metal salt solution, as this, as stated above, increases the strength of the particles. at After impregnation, the particles quickly absorb the solution by capillary action. This also leads to considerable Amounts of air enter and become trapped in the particles. If the strength is insufficient, the particles can under the the resulting pressures burst.

example 1

In this example the invention is illustrated on a laboratory scale in its preferred embodiment.

1000 g of silicon dioxide, 2168 g of boric acid and 470 g of sodium carbonate are prepared at 1250 ° C. with thorough mixing Produce a glass melt in a melting pot, stir the melt, keep it at 1250 ° C for one hour, lower the temperature to 1025 ° C. and the melt is stirred for a further 3 hours. The glass has. expressed by those serving to form it Oxides, the following composition:

SiO ₂ = 40% by weight

^B 2 ° 3 ⁼ ^ wt.% Na ₂ O = 11 wt.%

From the molten state, the glass is transferred into a frit by the fact that the melt as it leaves the Blowing the crucible with a stream of cold air. Sieve the frit and separate the fraction, which is passed through a No. 5 sieve of the U.S. Standard Sieve Series, on a No. 10 sieve of U.S. Standard sieve row, on the other hand, remains behind. Man then leaves the portion of the frit retained on the No. 5 sieve through a jaw crusher for the very large particles and a roll crusher for the smaller partial

309836/1120

to run. Again you separate those between sieve no.5 and the No. 10 sieve from the fraction.

The approximately 2 to 4 mm thick particles of the fractions separated and combined during sieving are added in one inclined rotating tube furnace of the type 54233 from Lindbergh Company, a subsidiary of Sola Basic Industries, Bead Shape ·. The tube furnace has a temperature in its central part of 1050 ° C. To prevent the glass particles from adhering to the clay lining of the tube furnace if it adheres, mix it to 74 parts by weight of the glass 1 part by weight Boron nitride too. The mixture is introduced into the tube furnace at one of its ends with the aid of a feed screw. More than 98% of the glass particles take on a pearl shape. she neither stick to each other nor do they stick to the wall of the tube furnace. After the treatment in the tube furnace, sieves the particles are repeated in order to separate from them the particles lying outside the desired size range, and then shake it to remove the boron nitride.

The pearls are filled in a ceramic bowl, heated to 480 ° C. and kept at this temperature for 5 hours. They are then broken down into a silicon dioxide-rich and a borate-rich phase.

After the heat treatment, the beads are allowed to cool to room temperature and are placed in tap water at room temperature containing reflux flask, using about 5 parts by volume of water to 1 part by volume of the beads, increases the temperature to 95 ° C in 4 hours and holds it for 12 hours to achieve a thorough washout this temperature .. Then you take the pearls out of the extract and pass it through at room temperature a cold trap in which about 80% of the borate salts are separated from the solution. The salts are dried and used they again for the production of glass melts. The water containing the non-precipitated part of the borate

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The solution is used to wash out further batches of phase-separated glass beads.

The beads separated from the extract are placed in an acid containing 0.3N hydrochloric acid at 95.degree. C. for treatment with an acid Reflux flasks using about 5 volumes of acid to 1 volume of the beads. One leads the Acid wash for about 5 hours. Then you take the Pearls out of the acid bath and rinses them in deionized water from hydrochloric acid and from any residues of the soluble phase remaining in the pores of the pearls. Man dry the beads in a forced air oven at 85 ° C to remove excess water and then heat them to Removal of chemically bound water to 760 ° C, holding it for one hour. The one for the physical Properties of the pearls determined are listed in Table II below.

Table II

Physical properties of the glass beads produced according to Example 1

Analysis

component Weight% SiO ₂ 98.18 B ₂ O ₃ 1.62 Na ₂ O 0.02 Al ₂ O 0.18

(Although Al ₂ O was not used in its manufacture, the analysis shows that the glass contains Al ₂ O ^, probably as a result of alumina inclusion in the SiO _2. )

Particle size 2-4 mm.

Bulk density of

compacted material 0.62 g / ccm

Pore volume 0.59 ccm / g

average pore size 100 - 120 S.

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surface
Compressive strength

230 m ² / g

2 2.5 kg / cm abs

(mean value of 20 samples)

after 1 hour Treatment at 980 ° C

surface
Surface loss
Volume shrinkage
Pore volume

Bulk density of
compacted material

Compressive strength

193 m ² / g

12%

16%

0.48 cc / g

0.69 g / cc

3.99 kg / cm abs

(mean value of 20 samples)

after 24 hours

Treatment at 980 ° C 170 m ² / g surface additional. 12% Surface loss additional 6% Volume shrinkage 0.40 cc / g Pore volume 5.04 kg / cm Compressive strength Example 2

Section

This example shows the improvement in physical properties of the invention through use a water wash and an acid wash compared to those of the same, but either only with Acid or glass bodies washed only with water.

Silicon dioxide, boric acid, sodium carbonate and alumina are made up of 45.4% by weight of SiO ₂ , 42.2% by weight of B ₂ O ^, 8.5% by weight of Na by thoroughly mixing these substances in suitable quantities ₂ O and 3.8% by weight .Al ₂ O, existing glass melt

309836/1 120

In the manner described in Example 1, the molten glass is first brought into particle form and then into the shape of pearls with a diameter of 1 to 2 mm. The beads are placed at a temperature of 500 ° C. for 64 hours off, let them cool to room temperature and wash them with 85 ° C tap water for 24 hours. One separates from these A certain amount of pearls washes them off from any residues of the soluble phase that may have remained in the pores and dry them at 85 ° C in a convection oven.

The other part of the pearls is filled in 1N hydrochloric acid containing reflux flask and carries out the acid wash for 24 hours at 95 ° C. Then you take the pearls out of the acid bath, it rinses with water of hydrochloric acid and in the pores any remnants of the soluble Phase free and dry them at 85 ° C in a convection oven.

In the same way as the first glass melt, a second one made of 45.0 wt.% SiO ₂ I, 43.3 wt.% B ₂ O, 7.7 wt.% Na ₂ O and 4.0 wt. % Al ₂ O, produces existing glass melt and, like the first melt, converts it first into particle form and then into pearl form. The beads are exposed to a temperature of 500 ° C. for 48 hours, allowed to cool to room temperature and then washed for 64 hours at 95 °. C with 1-N hydrochloric acid. The pearls are washed with water to remove hydrochloric acid and any residues of the soluble phase that may have remained in the pores.

In the following Table III are the physical properties the pearls treated by the process of the present invention and the pearls treated either with water only or with acid only recorded.

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■ ■. - after Weight% Table III porous glass beads, component Weight% Physical properties of the Water washing 91.7 Acid wash acid wash SiO ₂ 96.5 component 3.7 Example 2 produced Weight% B ₂ O ₃ 3.25 Analysis of the SiO ₂ 0.85 Water plus 96.6 Na ₂ O 0.05 porous beads B ₂ O ₃ 3.8 component 3.16 Al ₂ O ₃ 0.25 Na ₂ O mm SiO ₂ 0.01 1-2 mm Al ₂ O ₃ ccm / g B ₂ O ₃ 0.29 0.47 ccm / g 1-2 Na ₂ O 2 mm Particle size 0.38 Al ₂ O ₃ ccm / g Pore volume 1 - 0.45

surface

Surface after
16 hours at 850 ° C

Surface loss
Compressive strength

234 mVg

124 m ² / g 47% 1.54 kg / cm abs

253 m ² / g

173 m ² / g 31.6%

1.68 kg / cm abs

215 in / g

110 m ² / g 49%

1.12 kg / cm abs

Ca) CD

2309U9

Example 3

This example shows the degree to which deionized water is used to rinse the glass beads after the acid wash The thermal stability of the glass beads is increased compared to tap water.

According to the method described in Example 1, a _{glass melt consisting of 46.1% SiO 2} , 45.8% B ₂ O ^ and 8.0% Na ₂ O is prepared, the melt is conducted in particle form and the particles in the shape of pearls with a diameter of 1 to 2 mm, exposes the pearls to a temperature of 480 ° C for 5 hours, lets the pearls cool and then washes them first for 16 hours with tap water at 95 C and then for 6 hours with 0 , 3N hydrochloric acid at 95 ° C. The beads are rinsed in portions for 1, 3 and 5 hours either in running tap water or with deionized water at 95 ° C, dry> in the air and then put them in a for 16 hours Muffle furnace to a temperature of 950 ° C. The surface of the pearls is measured before and after the heat treatment. The measured values are recorded in Table IV below.

Table IV

Increase the thermal stability of the glass beads through the use of deionized water as a detergent

Thermal stability when the beads are used for 16 hours at 950 ° C; Size of the surface before

Ver
search Washing-up liquid before m ² / g later m ² / g 1 deionized water;
Rinsing time 1 hour 209 m ² / g 119 m ² / g 2 deionized water;
Rinsing time 3 hours 209 m ² / g 135 m ² / g 3 deionized water;
Flushing time 5 hours 209 m ² / g 137 m ² / g 4th Tap water;
Rinsing time 1 hour 209 m ² / g 62 m ² / g VJl Tap water;
Rinsing time 3 hours 209 m / g 55 m / g 6th Tap water;
Flushing time 5 hours 209 57

/ inn

Example 4

This example shows the influence that tin oxide in comparison to other metal oxides has on the thermal stability of the porous glass body according to the invention.

It provides in the manner described in Example 1, a 41.1 Gew.Si of SiO _2, 48.4 wt. # B ₂ O ,, 10 wt. ^C / o Ka ₂ O and 15 wt.% Al ₂ O , produces existing glass melt, converts the melt into particle form and the particles into the form of beads, separates the beads with a diameter of about 3.175 mm, exposes them to a temperature of 480 ° C. for 5 hours, allows them to cool and washes them first 16 hours in water at 95 ° C. and then 5 hours in 0.3 η hydrochloric acid at 95 ° C. The beads are then pre-shrunk by a two-hour treatment at bdi 980 ° C. According to the analysis, they contain 98.3 _{% by weight of SiO 2} , 1.39% by weight of B ₂ O, 0.025% by weight of Na ₂ O and 0.30% by weight of Al2 ° 3 ^{and have a} surface area of 200 m /G.

One of five portions of the beads is impregnated with a solution of SnCl ^ · 5H ₂ O, Al (NO,), · 9H ₂ O, CrCl, · 6H _{2 O or ZrOCl 2} · 8Η ₂ O and a portion is left untreated . The pearls contain 1.55 _{% SnO 2} , 1% Al ₂ O, 1.5% Cr ₂ O or 3% ZrO ₂ embedded in their pores. The samples are exposed to a temperature of 980 ° C. for a long time to determine their thermal stability. In Table V below, the measured values found are expressed by the percentage of their shrinkage.

Tabel V temperature shrinkage Heat treatment (o C) (Vol. 90 Used Time 980 10 Metal oxide (Hours.) 980 4th - 16 980 16 SnO ₂ 20th 980 10 Al ₂ O ₃ ; 20th 980 12th Cr ₂ O ₃ 20th ZrO ₂ 20th

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Claims (8)

1. A solid, thermally stable, microporous glass body, with a pore volume of at least 0.35 ccm / g, one Pore size in the range from 50 to 200 8 and an upper area of at least 100 m / g, characterized in that it a) at least 96% by weight SiO ₂ , b) less than 4% by weight B ₂ O ₅ , c) * less than 0.05% by weight of an alkali oxide and d) less than 0.4 wt.% Al ₂ O, contains, whereby this glass body has a compressive strength of Has at least 1.4 kg / cm abs and, 24 hours on one Heated temperature of 980 ° C, less than 30% of its original Area loses and by less than 25% of its Volume is shrinking. 2. Microporous glass body according to claim 1, characterized by a particle shape with a particle size of 0.05 up to 5 mm. 3. Microporous glass body according to claim 2, consisting of % SiO ₂ a) 97 to 99 wt. b) 1 to 3% by weight of B ₃ O ₅ c) 0 to 0, Q3 wt. % R ₃ O and d) 0 to 0.15 wt.% Al ₂ O ₃ where R stands for sodium or potassium. 4. Microporous glass body according to claim 3, characterized in that that it is 5 to 20%> of its original volume is pre-shrunk, a compressive strength of min- has at least 2.1 kg / cm abs and, heated to a temperature of 980 ° C. for 24 hours, shrinks less than 10% of its volume. 5. Microporous glass body according to claim 4, characterized by a metal oxide or noble metal layer deposited thereon. 309838/1120 mm. m & m 6. Microporous glass body according to claim 5, characterized in that that the metal oxide is tin oxide. 7. Microporous glass body according to claim 5, characterized in that that the noble metal is platinum or palladium. 8. Microporous glass body with a pore volume of 0.5 bJLs 0.7 cc / g and pore sizes in the range from 200 to 1000 pounds, characterized in that he a) at least 96% SiO ₂ by weight., b) less than 4 wt.% B ₂ O ^, c) less than 0.05% by weight of an alkali oxide and d) less than 0.4 wt.% Al ₂ O, contains, the glass body having a compressive strength of Has 0.35 to 1.4 kg / cm abs and, 24 hours of a temperature of 760 ° C, it shrinks by about 10 to 2096 of its volume. 9. Microporous glass body according to claim 8, characterized. records that it has particle shape with a size of 0.05 'up to 5 mm and off % SiO ₂ a) 97 to 99 wt. b) 1 to 3 wt.% B ₂ O, c) 0 to 0.03 wt. % R ₂ O and • d) 0 to 0.15 wt.% Al ₂ O, is composed, where R is sodium or potassium. 10. Microporous glass body according to claim 8, characterized in that that it has shrunk by 5 to 20% of its original volume. 11. Microporous glass body according to claim 8, characterized in that that a catalyst is embedded in it. 12. Microporous glass body according to claim 10, characterized in that that a catalyst is embedded in it. 309836/1120 13. Process for the production of a porous glass body with high thermal stability and low alkali content, characterized in that one .a). a phase-separable alkali-boron-lime glass onto a Heated temperature at which the glass forms two phases, one rich in borates and one in water Solution is soluble; * b) from the phase separated glass in a first stage the borate-rich phase washes out with water in such an amount that a porous glass is formed, and c) the alkali oxide and borate not removed from this porous glass during the treatment with water by washing dissolves with acid in a second stage and thus a microporous glass body with a low alkali borate content manufactures. 14. The method according to claim 13, characterized in that the phase separation is carried out over a time of 1 to 64 hours at a temperature of 420 to 700 ⁰ O. ' 15. The method according to claim 14, characterized in that the phase separation for the production of a porous glass body with a pore size in the range of about 50 to 200 S over a time of 1 to 8 hours at a Temperature from 420 to 500 ° C performs. 16. The method according to claim 14, characterized in that the phase separation for the production of a porous glass body with a pore size in the range of about 200 to 1000 S over a time of θ to 24 hours at a temperature of 580 to 650 ° C. 17. The method according to any one of claims 13-16, characterized in that that an aqueous solution of a metal borate is used for the water washing in the first stage. 309836/1120 18. The method according to any one of claims 13-16, characterized in that an alkali-boron-lime glass which can be separated into phases is used which contains 30 to 50% by weight of SiO ₂ , 40 to 55% by weight of B ₂ O ₃ , Contains 5 to 15% by weight of R ₂ O and 0 to 4% by weight of Al ₂ O ₃ If, where R is sodium or potassium. 19. The method according to any one of claims 13-16, characterized in that that the water wash in the first stage for about 4 to 24 hours at a temperature of about 40 to 95 ° C. 20. The method according to any one of claims 13-16, characterized in that that the acid wash in the second stage for at least 1/2 hour at a temperature of , 80 to 100 ⁰ C carries out. 21. The method according to any one of claims 13, characterized ; · Indicates that a mineral acid is used in the second washing stage used with a normality of 0.1 to 3. *. ■ · ■ · ■ 22. The method according to any one of claims 13-16, characterized in that that the extract obtained in the first stage is passed into a separating device, in which at least some of the alkali oxide and borate are separated from the water will; that the alkali oxide and the borate are dried and reused in the manufacture of glass melts and that the water is used again for a water wash in the first stage. 23 · Method according to one of claims 13 - 16, characterized in that that the vitreous body is rinsed with deionized water after treatment with a mineral acid. 24. The method according to any one of claims 13-16, characterized in that the porous glass body obtained after the two-stage treatment is allowed to shrink to increase its thermal stability by 5 to 20% of its original volume. 309936/1120 2309U9 25. The method according to claim 24, characterized in that heating the porous glass body to shrink in a HOE · here temperature, but must not be so high that the pores collapse in their entirety. 26. The method according to claim 25, characterized in that the porous glass body is exposed to a temperature of about 400 to 1000 ° C for up to five hours. Method according to claim 25, characterized in that after shrinking the porous glass body is treated with a solution of a zinc compound b to store tin oxide. 28. Glass mass for the production of a microporous glass body '' with high compressive strength and a low alkali oxide borate content, consisting of
30 to 50% by weight SiO ₂ ,
40 to 55 wt% B ₂ O ₃₁
'· 5 to 15 wt.% R ₂ O and. 0 to 4 wt.% Al ₂ O ,, where R stands for sodium or potassium. 29. Glass mass according to claim 28, consisting of 38 to 46% by weight SiO ₂ , 40 to 52% by weight B ₂ O ₃ and 8 to 12% by weight R ₂ O, where R stands for sodium or potassium. 309836/1120